Coatings play a useful role in the manufacture of a great many articles which find wide use in nearly all facets of contemporary life. Until recently, nearly all coatings were applied with employment of a hydrocarbon based solvent which evaporated leaving the dried coating on the article which was to be coated. This system met with increasing disfavor as the cost of energy needed to drive off the solvent at the rate required by industry increased, as the price of the organic solvent itself increased and as the deleterious environmental effects of the evaporated solvent became better understood. Systems aimed at solvent recovery to reduce pollution and conserve solvent have generally proven to be energy intensive and unacceptable.
In response, those skilled in the art have devised a class of coatings termed radiation-curable coatings. In one type of radiation-curing termed photocuring a solution of a photoinitiator in a reactive coating liquid is employed. The liquid approaches a pollution-free system as almost all of the liquid is converted to cured coating with little or no solvent emission upon the brief exposure of the coated substrate to ultraviolet light. The ultraviolet light equipment generally has a low demand for electrical energy and thus many technical and cost deficiencies caused by the pollution and energy problems of organic solvent systems are overcome.
As more and more applications for radiaton-curable systems are attempted there developed a need for greater varieties of radiation-curable contacts having differing characteristics in their properties both before and after curing. One such application, the use of photocurable coatings as varnishes over printing ink, requires the photocurable material to have a low viscosity before curing, cure rapidly upon exposure to radiation and have a high degree of gloss after curing. A radiation-curable coating having these characteristics would be of great advantage.